1. Field of the Invention
The present invention relates to a mouth guard-preparing sheet for the preparation of a mouth guard to be used for preventing teeth and their surrounding tissues from a trauma occurred mainly in sports.
2. Description of the Related Art
A large external force is often applied to teeth or a maxillary bone during the game of hard physical contact sports including boxing, rugby football and American football as well as soccer and karate. In order to confine a trauma on teeth and their surrounding tissues occurred at that time to the minimum and to protect a stomatognathic system, it is generally carried out to set an elastic material made of, for example, rubber, which is called a mouth guard or mouth protector, in an oral cavity.
As the mouth guard, a so-called “custom-made” mouth guard that a dentist makes according to the shape of an oral cavity of an individual for whom the mouth guard is set has become widespread. In the preparation of the so-called “custom-made” mouth guard, a mouth guard composition comprising a sheet-like polyolefin-based rubber material or thermoplastic resin (elastomer) such as an ethylene-vinyl acetate copolymer is used and formed using a heat-sucking type mouth guard preparation device provided with a heater and a sucking unit as shown in FIG. 4. In other words, a mouth guard-preparing sheet 1 provided in a sheet-like form is fixed within an exclusive fixed frame 2 coincident with the shape of the mouth guard-preparing sheet 1, heated and softened in 100˜150° C. for 2˜5 minutes by means of a heater 3 of 400 to 700 W generally provided in an upper portion, and pressed on a previously prepared gypsum cast 4 wherein a dentition and a gingiva in an oral cavity are reproduced, which is placed within a vacuum table 5 having many sucking openings 5a provided therein; and air between the mouth guard-preparing sheet 1 and the gypsum cast 4 is then sucked, thereby forming the mouth guard-preparing sheet 1 so as to coincide with the gypsum cast 4. There is thus prepared a mouth guard.
However, there was involved a problem that in preparing the mouth guard using the mouth guard-preparing sheet 1 in the above-describe method, an anterior teeth portion of the mouth guard after the formation becomes thin as shown in FIG. 5 that is a cross-sectional explanatory view. This is because in forming the heated mouth guard-preparing sheet 1 so as to coincide with the gypsum cast 4 while sucking, the mouth guard-preparing sheet 1 is elongated most in the anterior teeth portion which is the highest site on the gypsum cast 4, and as a result, the mouth guard in the anterior teeth portion becomes thin. The fact that the mouth guard in the anterior teeth portion becomes thin makes not only a problem of occurrence of tearing off of the mouth guard on the occlusion surface but also a decrease in the impact absorption capacity, which is caused by thickness on the occlusion surface becoming thin, as compared with that as originally designed. Accordingly, the resulting mouth guard cannot exhibit a sufficient effect.
In order to overcome the problem that the anterior teeth portion becomes thin, among conventional mouth guard-preparing sheets, there have been those which took an approach to make thick only the horseshoe-shaped portion corresponding to a dental arch portion. However, in these conventional mouth guard-preparing sheets, the dental arch portion is not always positioned at the center portion of the horseshoe-shaped portion, whose thickness is made thick, depending on the size of the gypsum cast and the shape of a jaw of an individual. For this reason, a mouth guard having a different thickness between the right and left sides thereof is likely formed. As a result, there was a problem that it takes a considerably long period of time to modify the formed mouth guard.